City T and City U are 556 km apart. At 6.21 p.m., Ahmad is travelling at a uniform speed left City T for City U while Luis set off from City U to City T along the same road at a uniform speed, which was 11 km/h slower than that of Ahmad. The two met at 10.21 p.m.
- Find the speed of Ahmad.
- If Luis continued to travel at the same speed, how long would it take for him to reach his destination after the two met? Express your answer in mixed number.
(a)
Time taken for Ahmad and Luis to travel from 6.21 p.m. to 10.21 p.m. = 4 h
Average speed of Ahmad and Luis
= 556 ÷ 4
= 139 km/h
Ahmad's speed
= (139 + 11) ÷ 2
= 150 ÷ 2
= 75 km/h
(b)
Luis's speed
= 75 - 11
= 64 km/h
Distance that Luis travelled in 4 h
= 4 x 64
= 256 km
Remaining distance that Luis needed to travel
= 556 - 256
= 300 km
Time that Luis needed to reach his destination after the two met
= 300 ÷ 64
= 4
4464 = 4
1116 h
Answer(s): (a) 75 km/h; (b) 4
1116 h